1. Field of the Invention
The present invention relates to improved hoppers and methods of making and using the same and, in particular embodiments, to such hoppers and methods for improved handling of particulate matter.
2. Description of Related Art
Early hopper designs typically were formed of a funnel-shaped housing of rigid, integral construction. A relatively large opening at the top of the housing served as an inlet and a smaller opening at the bottom of the housing served as an outlet.
One example of such a conventional hopper design is that shown at 31 in FIG. 1 of U.S. Pat. No. 3,147,144 to Wilhelm (issued Sep. 1, 1964). Wilhelm's hopper 31 is composed of a four walled structure, with each wall rigidly fixed to two adjacent walls to define a hollow housing having a rectangular horizontal cross-section, a rectangular opening or inlet at the top to receive particulate material P and an opening at the bottom to allow particulate material P to flow out of the housing.
According to its intended mode of operation, the particulate material P flows downward, by the force of gravity, from the top opening toward the bottom opening. However, certain particulate materials have a tendency to form a bridge spanning between two opposing hopper walls (wherein a plurality of closely packed particles forms a bridge or arch rigidly extending from one wall to an opposing wall) during the flow toward the bottom opening. Such particle bridges can restrict or stop the flow of particles through the hopper. In order to address this concern, Wilhelm employs a vibrator 32, mounted on the outside surface of each hopper wall, for imparting a vibrating motion intended to inhibit the formation of particle bridges.
Another conventional hopper design is that shown in FIGS. 1 and 2 of U.S. Pat. No. 3,261,592 to Dumbaugh, et al. (issued Jul. 19, 1966), wherein the hopper housing is formed of a partially cylindrical and partially conical shaped wall supported by resilient mounts 14. Dumbaugh et al.'s hopper is vibrated "from top to bottom along a horizontal path" by an exciter motor 19 mounted to the outside surface of the hopper wall.
In each of the hopper designs described in the above cited Wilhelm and Dumbaugh, et al. patents, the hopper housing is formed of a rigid walled structure to which a vibration imparting device is attached. Typically, in these types of rigid walled structures, vibrations imparted on one wall (or on a portion of the curved wall in the cylindrical and conical housing structure) are transmitted through the rigid structure to all of the walls (or to all other portions of the curved wall). In this regard, two opposing walls (or two opposing portions of a curved wall) will be affected by the same vibratory motion and, thus, may vibrate in the same or close phase and frequency, resulting in little or no relative motion between the two opposing walls (or two opposing portions of a curved wall). Without a suitable degree of relative motion between the two opposing walls (or two opposing portions of a curved wall), the ability of the vibrator to break apart or inhibit the formation of a particle bridge spanning between those opposed walls (or wall portions) is greatly diminished.
Another prior hopper design is that shown in FIG. 1 of U.S. Pat. No. 4,522,500 to Hyer (issued Jun. 11, 1985). Hyer's hopper includes a rigid walled housing 12 defining an open interior in which an agitator assembly 18 is located. The agitator assembly includes an agitator panel 20 situated internally of the hopper housing, a vibration imparting device 24 fixed to a frame 22 situated externally of the hopper housing and a pair of mounts 26 extending through the rigid wall of the hopper housing, coupling the frame 22 to the agitator panel 20. From Hyer's drawings, one can readily appreciate the complexities involved in coupling an externally located vibrator to an internally located moveable panel. Moreover, it would appear that such a design would be susceptible to problems associated with particles, dirt, or the like being trapped between the agitator panel 20 and the interior surface of the housing wall 12.
The above discussed prior hopper designs exemplify the need in the industry for a hopper which (1) has an improved ability for handling particulate material of the type having a tendency to bridge during its flow and (2) has a relatively simple construction. These needs are of particular importance in solid particle moving systems which require a sustained flow of particles to be maintained. For example, certain solids pump designs require, or perform better with, a sustained flow of particles entering the pump. Examples of such solids pump designs are described in U.S. Pat. No. 4,516,674 to Firth (issued May 14, 1985), U.S. Pat. No. 4,988,239 to Firth (issued Jan. 29, 1991) and U.S. Pat. No. 5,051,041 to Firth (issued Sep. 24, 1991), each of which are commonly assigned to the same assignee of the present invention and each of which are incorporated herein by reference. It is preferred that the hoppers which control the flow of particles entering such pumps be of the type which maintain a sustained, constant flow of particles and which minimize the occurrence of particle bridging or arching (which may cause flow interruptions).